This invention concerns the treatment of breast cancer or otherwise-sited cancer, and especially an efficient brachytherapy procedure for radiation treatment of tissue surrounding an arbitrarily shaped cavity resulting from following surgical tumor excision. Current brachytherapy methods of treating cancer of the breast, as well as cancer found in other areas of the human body with the patient under anesthesia, include surgical excision of the tumor (with some surrounding tissue) and then typically, after the surgical wound is closed, the patient is sent home pending determination of pathology of the excised tumor margin. Once clean margins are established, a radiation treatment plan is developed and the patient, in a series of later visits, is subjected to radiation treatment in the volume of tissue surrounding the excised tumor. This often involves re-opening the surgical cavity for insertion of an applicator to establish spatial relationships between the cavity and an ionizing radiation source or sources, e.g. radioactive isotopes, used to deliver the radiotherapy. Developing a radiation treatment plan under these circumstances is usually a several-hour process that can require external imaging of the excision cavity to determine its shape and location in the body using external devices such as magnetic resonance imaging, x-ray or CT scanning equipment. Transfer of data is then needed between the imaging equipment and the treatment planning software for preparing a plan of irradiation, with perhaps the need to verify transferred data values to check for errors. Often, the radiotherapy plan is divided into fractions (fractional treatments, the sum of which comprise the total treatment plan) which are separated in time to allow normal tissue to recover between fractions. Diseased tissue does not recover in this manner and therefore tends to be destroyed by the cumulative fractions. The entire prescription plan may require a few days or more to complete.
In the case of breast tumors, because breast tissue has great mobility, applicators are particularly important. The excision cavity may move if not properly supported, and spatial orientation may be lost between fractions. The applicator is therefore usually left inflated throughout the course of treatment, maintaining the spatial relationships built into the treatment plan.
There is also a need for increased precision in delivering radiation to a volume of tissue following surgery, to closely follow a physician's prescription which may vary from location to location within the resection cavity. For example, it may be necessary to reduce the dose to avoid damage to closely adjacent skin during irradiation of breast tissue, and/or to avoid damage to the heart, lungs and bones, while still delivering the full prescribed dose elsewhere. Over-radiation of any tissue is to be avoided as much as possible.
Recent advances in miniature x-ray tubes to replace isotopes for radiotherapy, and advances in rapid determination of resected tumor pathology, taken together, make intraoperative radiotherapy feasible. Regarding advances in pathology determination, see, for example, “Twenty Watts of Terahertz”, Eric J. Lerner, The Industrial Physicist, page 9, April/May 2003. See also “Development of Novel Technologies for In Vivo Imaging”, PAR-01-102, May 29, 2001, nih.gov website; “In Vivo Endoscopic Optical Biopsy with Optical Coherence Tomography”, Tearney, Brezinski, et al., Science, Vol. 276, Jun. 27, 1997, pp 2037-2039; “Oesophageal Histology Without a Biopsy”, Tudor Toma, The Scientist, Feb. 7, 2001, biomedcentral.com website; “Determination of Spatial Location and Pathology of Breast Lesions using Proton MRS”, imrr.org website; “Multiphoton Excitation Microscopy of Human Skin in Vivo: Early Development of an Optical Biopsy”, Barry R. Masters and Peter T. C. So, optics.sgu.ru website. Although the invention contemplates instant pathology supporting an intraoperative procedure, it should be understood that the invention also encompasses a procedure with delivery of radiotherapy following resection after an interval of up to a few weeks rather than as an intraoperative procedure.
Determination of pathology of tissue at the excision site is information the physician uses to determine whether further excision of tissue is required, or if the next step in treatment is radiation planning and delivery. The determination of a treatment plan depends on obtaining information on the shape and location of the excision cavity and any need to avoid damage to other areas of tissue (such as the skin, the chest wall, bones, lungs and heart). The planning process also requires that the emission characteristics of the radiation source be known. With this information, a therapy plan can be developed.
Proxima Therapeutics has developed a program for radiation treatment following tumor excision. In this procedure a breast tumor is excised, then a balloon applicator is inserted into the excision cavity (often through a new incision at the time of tumor excision or up to several weeks later). The applicator is expanded and the incision is closed except for a pigtail or spigot extending out of the breast for later use. At a later date, following determination of pathology, if no further excision is indicated, the patient returns for radiation treatment via the applicator. The Proxima applicator balloons are not capable of changing shape to accommodate irregularly-shaped cavities. The applicator balloons can be filled to the appropriate size for the particular cavity, but beyond this size variation adjustment is not possible. The surgeon therefore needs to cut as nearly matching an excision cavity as possible to enable the proper use of the device. This is often difficult.
With the applicator in the excision cavity and filled, the patient's breast is imaged by exterior imaging equipment. This imaging not only determines the size and location of the inflated applicator within the breast excision cavity, but also enables the physician to look at any gaps between the applicator and the tissue at the boundaries of the excision cavity. If the applicator/tissue contact is sufficient, the physician uses a table to look up the needed dwell time for the diameter of the applicator and for the particular activity of the radio isotope source, which is known. The ionizing radiation source, i.e. an iridium (192Ir) wire on the end of a stainless steel guide wire, is inserted into the middle of the applicator for the prescribed duration.
The Proxima procedure is based on a known geometry, e.g. a spherical shape of the applicator and cavity, and ideally, a substantially uniform isotropic iridium source. The equipment is not adaptable to an irregularly-shaped excision cavity, nor to prescription plans where skin, bone or other sensitive structures lie within the prescribed target tissue region. Moreover, the applicator and procedure are not useful for smaller-sized tumors, because of unacceptable surface-to-depth ratio of radiation dose at near ranges of the radiation source.
From the foregoing, it can be seen that there is a need to accommodate arbitrary resection cavity shapes and small cavities, to eliminate unnecessary patient or equipment transport for imaging, and easily to adjust delivered dose locally in order to spare sensitive tissue structures while treating diseased tissue adequately.
The following patent has some relevance to the present invention: European Patent Application EP1050321.